P963: EXTRAMEDULLARY MULTIPLE MYELOMA: CLINICAL CHARACTERISTICS, IMPACT, AND OUTCOMES IN A COHORT OF PATIENTS IN MEXICO
Authors: Amaya Llorente Chávez, Sergio Rodriguez-Rodriguez, Antonio Olivas Martínez, Cesar Omar Vargas-Serafin, Christianne Bourlon De Los Rios, Deborah Martínez Baños
Journal: HemaSphere (2023)

Topic: 14. Myeloma and other monoclonal gammopathies - Clinical Background: When a malignant axial mass is directly extended, extramedullary multiple myeloma (EMM) is categorized as osseous (EMMO) and as hematogenous (EMMH) when this dissemination takes place and results in an infiltration in an organ or tissue. It is well recognized that the prognosis and survival rate for EMM are dismal. It is unknown how EMM patients behave in Mexico. As far as we know this is the first EMM study in Mexico and Latin America. Aims: To define the prevalence, characteristics, overall survival (OS), and progression-free survival (PFS) of patients with EMM at the time of multiple myeloma (MM) diagnosis. Methods: A retrospective cohort study that included patients over the age of 18 diagnosed with MM in accordance with the International Myeloma Working Group criteria. A biopsy or imaging analysis was used to confirm the diagnosis of EMM. Results: Between 2006 and 2022, 301 participants with MM were included in the study; a total of 65 (22%) patients had EMM at the time of diagnosis of MM, 50 (77%) with EMMO, and 19 (29%) with EMMH, of which 4 (6%) had both presentations. Both imaging studies and biopsy were used for the diagnosis in 41 (48%) and 44 (51.7%) cases, respectively. The median number of EMMH organs that were affected was 2 (range 1-4). Involvement of the skin and subcutaneous tissue were the most prevalent, each one of them in 9 (17%) patients, followed by lymph nodes in 8 (15%), the lung and pleura in 7 (13%), and the liver and muscle in 4 (8%). It affected 2 (4%) patients in head, central nervous system, orbit, spleen, peritoneum, and kidney. The breast, heart, gut, genitalia, and gallbladder were the least frequent in 1 (2%) patient each. The majority of EMM patients (55.4%) were female and had an ISS of III (47.7%). Variables associated with EMM at the time of MM diagnosis were age < 64 years (p=0.042), a minor monoclonal peak of 2.7 g/dL (range 1.0-4.5) (p=0.041), light chain MM (p=0.014), a higher number of platelets of 240 x 103/mL (p=0.018) and glomerular filtration rate > 40 ml/min/m2 (p=0.004), higher albumin (p=0.026), lower amount of globulins (p=0.024), elevated β2 microglobulin of 5.2 mg/L (range 2.9-12.0) (p=0.004) and lower immunoparesis (p=0.043). EMMO was associated to light chain MM (p=0.02). Regarding the treatments given to EMM patients, 33 (55%) relied on thalidomide, 10 (16.7%) on an alkylating drug, and 17 (28.3%) on bortezomib. We compared the cases of MM vs. EMM at the time of diagnosis of MM. The OS of MM was 77.8 months (95% CI 56.9-98.7), EMMO 52 months (95% CI 18.9-85.3) and EMMH 32.7 months (95% CI 0-78.2), p= 0.012. EMMH vs. MM comparison yielded a p=0.05. PFS for MM was 28.2 months (95% CI 23.9-32.4), for the EMMO was 17.3 months (95% CI 7.2-27.4), and for the EMMH was 10.9 months (95% CI 7.8-13.9) (p < 0.001). Summary/Conclusion: In our population, the incidence of EMM was among the highest noted in the literature. This could be explained by a delayed referral to our Institution for diagnosis and treatment, or by the disease acting more aggressively in Mexican patients. The EMM offers a worse OS and PFS, and EMMH is the one that confers the poorest outcome. The disparities in our sample compared to other studies in the literature requires a multicenter investigation in Mexico to explore the clinical behavior and outcomes of EMM in Mexican patients.Keywords: Myeloma, Multiple myeloma